From: John <linux.kernel@free.fr>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, tglx@timesys.com, johnstul@us.ibm.com,
akpm@osdl.org, linux.kernel@free.fr
Subject: Re: One-shot high-resolution POSIX timer periodically late
Date: Wed, 07 Feb 2007 11:13:58 +0100 [thread overview]
Message-ID: <45C9A666.7010703@free.fr> (raw)
In-Reply-To: <20070206123716.GA8481@elte.hu>
Ingo Molnar wrote:
> John wrote:
>
>> Ingo Molnar wrote:
>>
>>> 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 too?
>>
>> Ingo, Thomas,
>>
>> I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an
>> apples-to-apples comparison because I get a tsc clocksource in
>> 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7.
>
> That suggests that the TSC was not deemed reliable by the newer kernel,
> which almost always means it's not realiable. I think the problems you
> were seeing are consistent with TSC being non-monotonic - so the fix is
> to not use the TSC - and the newer kernel does this automatically.
Ingo,
Perhaps you've mis-read my message?
*2.6.18.6-rt7* installed an acpi_pm clocksource. When I used a boot
parameter to force the clocksource to tsc, the high-resolution timer
infrastructure broke (timers expired several *ms* too late).
On the other hand, *2.6.20-rc6-rt6* and *2.6.20-rt2* both installed a
tsc clock source, and it works.
Therefore, it is not the newer kernel that ignored the tsc, but the
older kernel. Thus I don't know what to make of your comment :-)
Regards,
John
next prev parent reply other threads:[~2007-02-07 10:16 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <fa.4zD54Ie6Ozt0P4YqQSicS+XzXGw@ifi.uio.no>
[not found] ` <fa.G+/T32f2o1M3+YGLca/O8NaAQyY@ifi.uio.no>
[not found] ` <fa.6Ua8xjNfLKQEZZgDsoJgPMyww4g@ifi.uio.no>
[not found] ` <fa.yQlV+WU0TgrJTVqjopa01tgCnT0@ifi.uio.no>
[not found] ` <fa.ucVrLJ1Lh6FjdBHRglsIUc8/evk@ifi.uio.no>
[not found] ` <fa.Id9oufyELrVbe5Wb8SRakwC0V50@ifi.uio.no>
2007-02-01 10:18 ` One-shot high-resolution POSIX timer periodically late John
2007-02-06 12:37 ` Ingo Molnar
2007-02-07 10:13 ` John [this message]
2007-02-05 16:37 ` John
2007-02-06 7:31 ` Peter Zijlstra
2007-02-07 10:25 ` John
2007-02-08 17:32 ` Thomas Gleixner
2007-02-09 15:25 ` John
2007-02-09 16:21 ` Benedikt Spranger
2007-02-09 16:43 ` Thomas Gleixner
[not found] <fa.mtUvfgenNQkCc8835prYbwyiPQs@ifi.uio.no>
[not found] ` <fa.lwkMc548uRMcUjd9KZ2pC1DMKT4@ifi.uio.no>
[not found] ` <fa.dTtI0ctv1nu+tCWiK6jGPnrX69k@ifi.uio.no>
[not found] ` <fa.CMU3scpnLxfHVWRFPcmfRl2CjhA@ifi.uio.no>
2007-01-30 17:38 ` John
2007-01-30 20:25 ` Ingo Molnar
[not found] <fa.NwnlFyMPfa3XG6my3HKGWnCW3x4@ifi.uio.no>
[not found] ` <fa.Ji4GnAbBF2FR5JbSxvxn2haJZIk@ifi.uio.no>
2007-01-25 9:59 ` John
2007-01-25 22:19 ` john stultz
[not found] ` <fa.8TBiwbgs8B881k+3X+IlFjhqpLI@ifi.uio.no>
2007-01-25 12:03 ` John
[not found] <45B729AF.4030701@privacy.net>
2007-01-24 19:02 ` john stultz
2007-01-24 20:09 ` Ingo Molnar
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